1. Field of the Invention
An aspect of the present invention relates to a centrifuge which, while charging a liquid sample continuously into a rotor, rotates the rotor at a high speed to centrifuge micro-particles contained in the liquid sample.
2. Description of the Related Art
As a centrifuge of this type, there are known a centrifuge which is disclosed in the JP-UM-S48-028863-B for centrifuging a virus contained in a liquid medium, and continuous centrifuges respectively disclosed in the JP-H07-106328-B and JP-2004-322054-A in which a sample to be centrifuged is centrifuged in a state where it is isolated from the open air.
Here, description will be given below of a conventional centrifuge with reference to FIGS. 8 and 9.
FIG. 8 is a perspective view of a conventional centrifuge, and FIG. 9 is a longitudinal section view of a rotation device portion of the centrifuge. The centrifuge shown in these figures is a centrifuge of a type which charges a liquid sample continuously into a rotating rotor 14 and centrifuges the liquid sample. And, this centrifuge is used to centrifuge a virus, a culture cell, a culture fungus body and the like in large quantities to purify mother materials which are used for vaccines and medicines.
FIG. 8 shows a state of a cylindrical rotor 14 in which it hangs down before it is stored into a chamber 10, and in this figure, a rotation device portion 101 includes a lift mechanism 13. Here, the lift mechanism 13 includes a drive portion 12 for mounting and removing the oblong rotor 14. And, the lift mechanism 13 not only can lift, advance and lower an upper plate 17 together with the rotor 14 mounted on the rotation shaft 21 of the drive portion 12 but also, in a state where they are advanced and lowered, can mount and remove the rotor 14.
A control device portion 3 includes a power supply for the drive portion 12 for driving the rotation device portion 101, and a vacuum pump for depressurizing the chamber 10. The control device portion 3 supplies cooling water or the like for cooling mechanical seals 24 and 25 (see FIG. 9) respectively serving as a charge/discharge portion for charging and discharging the cooling water of the lower bearing portion 23 as well as refrigerants and samples which flow in a cooling coil for cooling the rotor 14. Also, the control device portion 3 incorporates therein a controller (not shown) for controlling a power supply and an electric signal necessary for driving it, and further includes a control panel 31. The control panel 31 not only can set the speed of revolutions, the time of rotation, temperature and the like functioning as the operating conditions of the present centrifuge, and can display the operating state of the centrifuge, but also includes a switch which can be used to start and stop the operation of the centrifuge. Further, although not shown, the control device portion 3 includes therein a hydraulic unit which includes a refrigerator for cooling cooling water, a refrigerator for cooling refrigerants used to cool the rotor 14, a hydraulic pump for driving the lift mechanism 13, a control valve and the like.
Also, a pipe/electric wire connecting portion 4 is a connecting portion which is used to control the connection of the electrical parts, the supply of the cooling water and refrigerants, the depressurization operation and the like in order to operate the rotation device portion 101 from the control device portion 3.
FIG. 9 shows a longitudinal section view of the main portion of the rotation device portion 101 of the centrifuge, in which the cylindrical rotor 14 disposed in the vertical direction of the centrifuge is supported by two hollow upper and lower rotation shafts 21 and 22 respectively extended in the axial direction of the rotor 14, while the interior of the rotor 14 and the hollow portions of the rotation shafts 21, 22 cooperate together in forming a continuous liquid flow passage.
Also, in the interior of the rotor 14, there is disposed an exchangeable core 28 including a plurality of circumferentially equally divided blade-shaped partition walls respectively provided on and projected from the outer peripheral portion thereof, while this core 28 forms a flow passage for a sample. The upper rotation shaft 21 is connected to the drive portion 12; and, to the upper rotation shaft 21, there can be transmitted a drive force for driving and rotating the rotor 14. The lower rotation shaft 22 is rotatably supported not only by a sliding bearing (plain bearing) which is used to center the rotor 14 and dampen the rotational vibrations thereof but also by a lower bearing portion 23 which is provided on the outer peripheral portion of the lower rotation shaft 22 and includes a damper. By the way, the upper and lower bearings are lubricated with lubricant and, while the rotor 14 is rotating, a very small amount of lubricant leaks out to the chamber 10 side and collects in the bottom portion of the chamber 10. In order to collect this waste lubricant after stop of the operation of the rotor 14, there is formed a small hole in the bottom of the chamber 10 and, on the open end of the small hole, there is provided a drain valve 30.
Further, on the end portions of the upper and lower rotation shafts 21, 22, there are provided the mechanical seals 24 and 25 respectively. Thus, even while the rotor 14 and rotation shafts 21, 22 are rotating at high speeds, the liquid samples are allowed to flow through these mechanical seals 24 and 25 and, in order to cool the mechanical seals 24 and 25, there flows a coolant around the mechanical seals 24 and 25. Each of the mechanical seals 24 and 25 includes a rotation shaft side member, a non-rotating fixed seal, a spring for bringing the fixed seal into contact with its associated rotation shaft 21 (22), and the like. This structure makes it possible for the liquid sample to flow even while the rotation shafts 21 and 22 are rotating at high speeds.
On the periphery of the rotor 14, there is wound a cooling coil 15 which is used to cool the rotor 14; on the outside of the cooling coil 15, there is disposed a defense wall (protector) 16; and, the chamber 10 is disposed in such a manner that it surrounds these members. The chamber 10 cooperates with a base 11 disposed downwardly of the chamber 10 and an upper plate 17 (which also serves as the support member of the drive portion 12) in constituting a vacuum chamber. The chamber 10 can be depressurized from the pipe connecting port that is formed in the barrel portion of the chamber 10, while the rotor 14 can be driven and rotated within the depressurized chamber 10.
In the above-structured centrifuge, the liquid sample to be centrifuged is supplied from the connector portion 26 (or 27) of the rotation device portion 101 by delivery means such as a pump (not shown), is introduced through the rotation shaft 21 (or 22) into the rotor 14, and is centrifuged within the rotor 14 due to a strong centrifugal force applied thereto; and, the supernatant of the liquid sample is discharged therefrom through the other rotation shaft 22 (or 21), mechanical seal 25 (or 24) and connector portion 27 (or 26). And, the discharged liquid sample after centrifuged is collected into a storage vessel (not shown) or the like.
The sample to be treated in the thus structured centrifuge includes, for example, an influenza virus, a Japanese encephalitis virus, a whooping cough virus, an AIDS virus, a hepatitis virus and the like. The parent material of such sample is obtained by floating, on a liquid, a culture medium, a cell or a body fluid taken from an animal, and the like. The sample is centrifuged and rectified using the present centrifuge and is used as the material of a vaccine and a medicine. Careful attention must be paid to such sample in order to prevent other viruses or impurities from mixing with such sample to contaminate it. In the medical manufacturing field and in the medical field, as means for sterilizing bacteria and various kinds of minor germs adherent to medicine manufacturing machine and instrument, there is often used steam sterilization (which is also referred to as autoclaving).
However, in the centrifuge, such steam sterilization is not enforced owing to the structural limit thereof and owing to the limit of the material of the parts thereof, but there is employed exclusively a method for sterilizing the centrifuge using a bath. The bath sterilization is not sufficient, because some of baths have no effect on some of bacteria and various kinds of minor germs. Also, when such bacteria and minor germs come into contact with the composing parts of the centrifuge, it has been found that they can corrode or degenerate the composing parts.
On the other hand, the steam sterilization has a wide effective range and has a sterilization effect on most of bacteria and various minor germs, and also the sterilization effect can be obtained by heating using steam. Therefore, when the composing parts of the centrifuge have heat resisting properties, the steam sterilization can be applied. Recently, as disclosed in the JP-2004-322054-A, it has been able to apply the steam sterilization also to a continuous centrifuge structured such that a steam sterilizable metal-made core is inserted into a rotor provided in the centrifuge.
Also, in the JP-2001-321699-A, there is proposed a technology which, in a centrifuge capable of treating an inflammable sample, measures the oxygen density of the interior of a rotor filled with an inert gas and, when the measured oxygen density exceeds a given value, stops the drive device of the centrifuge.
When steam sterilization is enforced on a centrifuge with a cylindrical rotor mounted thereon, the steam sterilization temperature is set at lowest at a temperature of 115° C., in most cases, at a temperature of 121° C. at which a higher effect can be obtained. Thus, it takes long time to cool the cylindrical rotor from such high temperatures down to the temperature range of 4° C.˜room temperature which are the temperatures necessary for the centrifugal separation, resulting in the very poor centrifuging operation efficiency.
As a solution to the above problem, there is known a method in which a liquid of a low temperature is charged into a cylindrical rotor to cool the rotor. In this method, however, when the charged liquid boils or evaporates at a high temperature, in some cases, there is generated an inconvenience that impurities contained in the liquid or the compositions of the liquid stick to the surface of the rotor and the surfaces of the sample flow passage composing parts of the centrifuge and provide the contamination source of the sample when the sample is used later.